| Term | Definition |
|---|
| Relative Age | the age of an object in relation to the ages of other object |
| Absolute Age | the numeric age of an object or event, often stated in years before the present, as established by an absolute-dating process, such as radiometric dating |
| Fossil types | imprints, molds and casts, coprolites, gastroliths |
| Principle of Uniformitarianism | a principle that geologic processes that occurred in the past can be explained by current geologic processes |
| Principle of superposition | new sedimentary rock on top of older rocks. in a sequence, oldest rocks will be on the bottom and youngest will be on the top |
| Law of original horizontality | sediments are laid down in flat, horizontal layers and those layers will remain flat unless disturbed |
| Law of Cross-cutting relationships | if a feature cuts through another, the feature that cuts is younger |
| Index fossils | a fossil that is used to establish the age of a rock layer because the fossil is distinct, abundant, and widespread amd existed for only a short span of geologic time |
| Half-life | the time required for half of a sample of a radioactive isotope to break down the radioactive decay to form a daughter isotope |
| Radiometric Dating | a method of determining the absolute age of an object by comparing the relative percentages of a radioactive (parent) isotope and a stable (daughter) isotope |
| imprints | carbonized imprints of leaves stems, flowers, and fish made in soft mud or clay preserved in sedimentary rock |
| molds and casts | shells often leave empty cavities called molds within hardened sediment |
| coprolite | fossilized dung or waste materials from ancient animals |
| gastrolith | stones from dinosaur's digestive systems to help them grind their food |
Combine with other sets
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